Hard to know. Maybe both of them will exist in the future. There are still many people can not access the computer or technology which allow them to use the digital money
Well when all people all over the world will adopt how to used digital money i am definitely sure that it has a big chance that the cash or the paper money will dissapear in this world, but i think cash will still stay in this world for long time because until now not all people is supporting digital money.
All we need is to hold valuable currency either in physical form or in digital form; we know that the most valuable currency is the Bitcoin so we are very happy with it as it is working more for us. It is of less importance if you have quantity of less valuable currency that will work less for you. So it is up to the value and even all of us here desire for valuable coin and not less valuable currency.